1. Field of the Invention
The present invention relates to a nebuliser for a fluid having a conveying tube for conveying the fluid, wherein in particular the conveying tubeis constructed as a thick-walled capillary and a method of producing a thick-walled capillary.
2. Description of Related Art
A nebuliser available under the trademark RESPIMAT® in the form of an inhaler is known, and is illustrated in its basic form in International Patent Application Publication WO 91/14468 A1 (U.S. Pat. No. 5,662,271) and in a specific configuration in International Patent Application Publication WO 97/12687 A1 (U.S. Pat. Nos. 6,918,547 and 6,726,124) as well as in FIGS. 1 & 2 of the accompanying drawings of this application. The nebuliser has a conveyor device with a conveying tube for conveying and atomising the fluid. The conveying tube is constructed, in particular, as a thick-walled massive capillary, as shown in FIG. 3b of WO 97/12687 A1. The conveying tube is therefore very difficult and complex to produce.
Capillaries with a small internal diameter and thin walls are generally obtainable. Capillaries with a thick wall and small manufacturing tolerances are, however, very difficult to produce and often have undesirably rough inner walls. This can be explained by the many forming steps (which are often, in the last analysis, carried out without a core because of the small internal diameter), needed to produce a thick-walled massive capillary.
In the present application the term “capillary” relates, in particular, to microfluidic, preferably, elongate structures with a hydraulic diameter of less than 1000 μm, particularly, preferably, less than 500 μm. The internal cross-section is preferably, but not necessarily, at least essentially round. The same is true, in particular, of the outer contour of the preferably, tubular or cylindrical capillary. However, the capillary may also have other non-round internal and/or external cross-sections or contours.
The term “thick-walled” refers herein to a capillary, particularly, when the mean inner diameter is less than 50% of the outer diameter, particularly, less than 30%, and/or when the wall thickness is more than 0.3 mm, preferably, more than 0.5 mm.